wip(assembler): round L19 -- strate ceilings closed at every LOD; ledges diagnosed

The shared boundary-cap path now emits a cap wherever the field is solid just below a strate's
configured top (it previously required a solid-to-air crossing there) and checks a 5x5 perimeter
grid before suppressing a fallback cap. Strict audit: 0 misses / 0 edge gaps, LOD0-8.
farHorizonVersion 3 -> 4. SurfaceWorld LOD0-2, full detail and exact queries unchanged; 28/28
matrix plus 14/14 crossing; route parity and proofs pass.
Ledges: the lower stratum's terrain at the FI/SW interface, seen through the FI void, sampled at
0.5/1/2 m at LOD1-3 (up to 1.5 m / 7.7 m ring steps). Fix deferred to the units/layers round.

Co-Authored-By: Claude Opus 5.5 <noreply@anthropic.com>
Claude-Session: https://claude.ai/code/session_01CSFYgsdW8ejZSyiMf4qRSX

Standalone/Research/WorldAssemblerM3/Linux19/RunCrossingL19.py

@@ -0,0 +1,81 @@
+#!/usr/bin/env python3
+"""Run the L19 24 m SurfaceWorld crossing hash matrix."""
+import os
+import re
+import signal
+import subprocess
+import time
+from pathlib import Path
+
+ROOT = Path(__file__).resolve().parents[4]
+OUT = ROOT / "Saved/Linux/l19-crossing"
+OUT.mkdir(parents=True, exist_ok=True)
+if not os.sched_getaffinity(0).issubset(set(range(12))):
+    raise SystemExit("run under taskset -c 0-11")
+BINARIES = {
+    "clang-off": ROOT / "Standalone/bin/linux/VoxelForgeCoreHeadless-linux19-clang",
+    "gcc-default": ROOT / "Standalone/bin/linux/VoxelForgeCoreHeadless-linux19-gcc",
+}
+PATTERN = re.compile(r"^\[Pipeline(?:FullDetailHash|WholeViewHash|LODHash|ExactQueryHash)\].*$", re.M)
+RUNS = [(1, 1), (8, 1), (12, 1), (12, 2), (12, 3), (12, 4), (12, 5)]
+passed = True
+for compiler, binary in BINARIES.items():
+    reference = None
+    for workers, repeat in RUNS:
+        name = f"{compiler}-w{workers}-r{repeat}"
+        logfile = OUT / f"{name}.log"
+        command = ["prlimit", "--as=6442450944", "--", str(binary),
+            str(ROOT / "Standalone/data/owner_world.json"),
+            "--world-assembler-prototype", "--stream-benchmark", "--stream-pipeline",
+            "--stream-hash", "--force-generate", "--clip-radius=3", "--max-clip-level=8",
+            f"--workers={workers}", "--camera=0,-35,-487.94,0,-22",
+            "--camera-step=24,0,0", "--region-crossing", "--recipe=surface-world"]
+        started = time.monotonic()
+        peak_rss = 0
+        timed_out = False
+        with logfile.open("w", encoding="utf-8") as stream:
+            process = subprocess.Popen(command, stdout=stream, stderr=subprocess.STDOUT,
+                                       start_new_session=True)
+            while process.poll() is None:
+                pending, seen = [process.pid], set()
+                while pending:
+                    pid = pending.pop()
+                    if pid in seen:
+                        continue
+                    seen.add(pid)
+                    try:
+                        pending.extend(int(value) for value in
+                            Path(f"/proc/{pid}/task/{pid}/children").read_text().split())
+                        for line in Path(f"/proc/{pid}/status").read_text().splitlines():
+                            if line.startswith("VmRSS:"):
+                                peak_rss = max(peak_rss, int(line.split()[1]))
+                                break
+                    except (FileNotFoundError, PermissionError, ProcessLookupError, ValueError):
+                        pass
+                if time.monotonic() - started > 900:
+                    os.killpg(process.pid, signal.SIGTERM)
+                    try:
+                        process.wait(timeout=5)
+                    except subprocess.TimeoutExpired:
+                        os.killpg(process.pid, signal.SIGKILL)
+                        process.wait()
+                    timed_out = True
+                    passed = False
+                    break
+                time.sleep(0.1)
+            code = process.wait()
+        elapsed = time.monotonic() - started
+        hashes = PATTERN.findall(logfile.read_text(encoding="utf-8", errors="replace"))
+        ok = code == 0 and not timed_out and len(hashes) == 12
+        if reference is None:
+            reference = hashes
+        elif hashes != reference:
+            ok = False
+            print(f"[CrossingMismatch] {name}", flush=True)
+        passed &= ok
+        print(f"[CrossingRun] {name} exit={code} seconds={elapsed:.3f} "
+              f"peak_rss_kib={peak_rss} hash_rows={len(hashes)} "
+              f"status={'PASS' if ok else 'FAIL'}", flush=True)
+print(f"[CrossingSummary] rows={len(BINARIES)*len(RUNS)} expected=14 "
+      f"result={'PASS' if passed else 'FAIL'} path={OUT}", flush=True)
+raise SystemExit(0 if passed else 1)